Conventionally, there has been known a siphon jet toilet in which a jet spout port 132 extending rectilinearly toward a center of an inlet portion 122a of a water discharge trap conduit 122 is disposed in order to perform startup of a siphon and discharge of waste efficiently by a jet spout water flow from the jet spout port in the siphon jet toilet, as shown in Patent Document 1 (Japanese Patent No. 5429688) and Patent Document 2 (Japanese Patent No. 4529178).